1. Continue to develop towards high speed and high rigidity

With the development of related technologies such as spindle bearings and their lubrication technology, precision machining technology, precision dynamic balancing technology, high-speed cutting tools and their interface technology, high-speed electric spindles for CNC machine tools have become a common development trend. In terms of the stiffness of the electric spindle system, due to the development of bearings and lubrication technology, the stiffness of the electric spindle system is increasing, meeting the needs of CNC machine tools for high-speed, high-efficiency, and high-precision machining.

2. Developing towards high-speed, high-power, low-speed, and high torque direction

According to actual usage needs, most CNC machine tools need to be able to meet the requirements of heavy cutting during low-speed rough machining and precision machining during high-speed cutting. Therefore, the machine tool electric spindle should have the performance of low-speed high torque and high-speed high power.

3. Further develop towards high precision, high reliability, and extended working life

Users have increasingly high requirements for the accuracy and reliability of CNC machine tools. As one of the core functional components of CNC machine tools, the electric spindle has increasingly high requirements for accuracy and reliability. If the radial runout of the spindle is less than 0.001mm, the axial positioning accuracy is less than 0.5 µ m. At the same time, due to the use of special precision spindle bearings, advanced lubrication methods, and special preload application methods, the service life of the electric spindle is correspondingly extended, and its reliability is increasing. Step Tec's electric spindle is also equipped with an acceleration sensor to reduce the vibration acceleration level of the bearings. In order to monitor and limit the vibration on the bearings, a vibration monitoring module is installed to extend the working life of the electric spindle.

4. The built-in electric motor of the electric spindle has diverse performance and forms

In order to meet the needs of practical applications, the performance of the electric spindle motor has been improved, and the ratio of the constant torque high-speed output of the spindle motor to the constant power high-speed output (i.e., the constant power speed regulation range) has reached 1:14. In addition, the appearance of permanent magnet synchronous motor electric spindles has made synchronous motor electric spindles smaller in size compared to asynchronous motor electric spindles of the same power, which is conducive to improving power density and achieving small size and high power.

5. Fast start and stop response speed improvement

In order to shorten the auxiliary time and improve efficiency, it is required that the start stop time of the CNC machine tool electric spindle be as short as possible, so it is necessary to increase (reduce) the start and stop speed. At present, the starting and stopping acceleration of foreign machine tool electric spindles can reach over 1g, and the full speed starting and stopping time is less than 1s.

6. Diversified bearing and its preloading application modes, lubrication modes

In recent years, in addition to traditional steel rolling bearings, ceramic ball hybrid bearings have also been widely used. Lubrication methods include grease, oil mist, oil air, etc., especially oil air lubrication (also known as oil air), which has the characteristics of adapting to high speed, environmental protection and energy saving, and has been widely promoted and applied; In addition to rigid preload (also known as positioning preload) and elastic preload (also known as constant pressure preload), an intelligent preload method has been developed for rolling bearings, which uses hydraulic cylinders to preload the bearings. The preload can be controlled according to specific working conditions such as spindle speed and load, making the bearing support performance better. In the field of non-contact bearing supported electric spindles, a series of products such as magnetic bearings, air bearing electric spindles, liquid bearing electric spindles, etc. have been supplied to the market.

7. The tool interface is gradually moving towards HSK and Capto tool holder technology

After the high-speed machine tool spindle, the traditional CAT (7:24) tool holder structure can no longer meet the requirements of use due to centrifugal force, and other tool holder interface forms that meet high-speed requirements such as HSK (1:10) need to be used. HSK tool holders have outstanding static and dynamic connection rigidity, large torque transmission capability, high tool repeatability and connection reliability, making them particularly suitable for use in high-speed and high-precision situations. Therefore, HSK tool holder interface has been widely used in high-speed electric spindles. In recent years, the Capto tool interface proposed by the company has also been applied in the machine tool industry. Its basic principle is similar to the HSK interface, but its torque transmission ability is slightly larger. The disadvantage is that the inner hole of the spindle end is difficult to machine and the process is more complex.

8. Developing towards multifunctionality and intelligence

In terms of multifunctionality, there are technologies such as angular stop precision positioning (quasi stop), C-axis drive, hollow air blowing for tool change, hollow coolant, shaft end gas seal, low-speed torque amplification, axial positioning precision compensation, and automatic dynamic balance technology for tool change. In terms of intelligence, it is mainly manifested in various safety protection and fault monitoring and diagnosis measures, such as tool change interlock protection, bearing temperature monitoring, motor overload and overheating protection, bearing unloading protection when loosening the tool, spindle vibration signal monitoring and fault abnormal diagnosis, automatic compensation for axial position changes, signal monitoring and automatic control during grinding wheel dressing, and tool wear and damage signal monitoring. For example, the Step Tec electric spindle is equipped with a diagnostic module, and maintenance personnel can read data through infrared interface correlation, identify overload, and calculate the working life of the electric spindle.